Abstract: The Al-Zn-Cu-Mg aluminum alloys are used as materials for transportation vehicles such as automobiles and aircrafts because of their high strength and light weight. This alloy has a low productivity and poor extrusion characteristics because this alloy has segregation and heterogeneous structure by addition of a lot of elements. This billet by the conventional DC process can’t avoid weak dendrite, segregation and hot cracks. This problem can be solved by applying Magneto Hydro Dynamic(MHD) technology. MHD is not a simple agitation technique like the existing EMS, but it is a more powerful and combines technology such as stirring, vibration and acoustic wave. The grain size of the 7 inch billet by DC casting shows large and uneven structure of 420μm. However the billet by MHD treatment is fine and uniform at 90μm, the dendrite changes to equiaxed structure and a sound billet without hot crack can be produced.
In this study, the original equipment and methods for the MHD macro/microstructure managed formation in the crystallizers of continuous casting processes by the applying of the amplitude modulated(AM) pulse magnetic fields (PMF) it the electromagnetic stirrer(EMS) has been developed and tested. MHD method has provide the complex electrodynamic, hydrodynamic and acoustic pulse-force processing of unsolidified casting product portion for providing equalizing of solidification front in the billet mushy zone.
Authors: K.H. Kim, M.A. Slazhniev, S.W. Kim, W.J. Kim, and H.S. Sim
Keywords: Microstructures, Magneto Hydro Dynamic treatment, Grain refinement, Segregation, continuous casting